The invention relates to a device for testing dynamic frictional coefficients, which is applicable to the multi-axial stress condition in the shaping process of pipe expanding and belongs to the technical field of material processing. The device comprises a digital control machine tool holder, a frictional head, a hard rubber pad, a specimen fixing platform, a fixing platform support, a piezoelectric sensing platform of a three-phase dynamometer, a charge amplifier, and an A/D collecting computer, wherein the frictional head is arranged under the digital control machine tool holder, testing specimens are fixed on the specimen fixing platform through the hard rubber pad, the specimen fixing platform is arranged on the fixing platform support, the lower end of the fixing platform support is two swallow-tail shape surfaces which incline downward swallow-tail shape slots are arranged on the two inclined surfaces along the inclined direction, the upper portion of the fixing platform support is an upper inclined surface which is matched with the specimen fixing platform, swallow-tail shape bosses are arranged evenly on the upper inclined surface along the inclined direction, the swallow-tail shape bosses are matched with the swallow-tail shape slots, the fixing platform support is fixed on the piezoelectric sensing platform, and the piezoelectric sensing platform is connected with the A/D collecting computer through the charge amplifier. The invention has simple structure, convenient operation, high accuracy, and strong versatility.